Compound resin compositions having high degree of mechanical strength have been required in a variety of fields. Resin rigidity, thermal resistance and impact resistance have been improved by dispersing a filler in the resin. In particular, many attempts have been made to improve mechanical properties and thermal resistance by dispersing a filler in molecular form in a polymeric material.
For example, Japanese Patent Application, First Publication No. Hei 2-10226 discloses a technique in which an intercalated compound is formed by inserting an organic cation between the layers of a stratified clay mineral, opening the distance between the layers. At this point, monomer is inserted and then polymerized. Using the polymerization energy at this time, the intercalated compound is dispersed in molecular form.
In this method, the organic cation in the polycondensation reaction of polyamide, polyester or the like, may be substituted by a monomer hydrochloride, or intramolecular cyclic salts, carboxylic monoester or the like.
A second method is known in which an attempt is made to disperse a stratified clay mineral in molecular form by using an organic cation to swell the stratified clay mineral in advance, and then subjecting the clay mineral to infinite swelling using an organic solvent, so that the stratified clay mineral takes on a house-of-cards structure. The stratified clay mineral is then dispersed in molecular form by bringing it into contact with a melted polymer.
However, the former of these two methods, while dispersing the filler with good efficiency, requires equipment for polymerization. Accordingly, production costs rise, so that this method cannot be viewed as economical. This reaction is currently employed in polyamide and polyester which are condensation polymerization systems. In addition, in heat-cured resins, the reaction is limited to radical polymerization or cation polymerization of the type in which a reactive monomer is inserted into the layers and then polymerized. Since the monomer inserted between the layers must be one which exists stably therein, the monomer employed is limited to liquid monomers. Accordingly, this first method has a drawback in that it provides only limited resin materials having a low filler density when obtaining a compound resin composition in which a filler is dispersed in molecular form. As a method to improve these circumstances, as disclosed in Japanese Patent Application, First Publication No. Sho 63-230766, Japanese Patent Application, Second Publication No. Hei 7-47644, Japanese Patent Application, First Publication No. 7-70357 and the like for example, the aforementioned second method proposes bringing the clay mineral into contact with a solvent. The infinitely swelled clay mineral is then directly dispersed in the polymer by bringing it into contact with a hydrophobic resin. However, a large amount of organic solvent must be used in methods of this type. In addition, even if the employed organic solvent contributes to infinite swelling, solubility between the polymer and organic solvent may be poor depending upon the polymer employed. In this case, it may not be possible to disperse the infinitely swelled stratified mineral in the polymer due to the infinitely swelled stratified mineral's affinity to the organic solvent. This type of polymer has very poor affinity with the solvent, even if the resin is melted. As a result, the infinitely swelled layered mineral formulated in advance by treatment with an organic cation has poor affinity and is difficult to disperse, even if brought into contact with a melted liquid polymer, so that complete dispersion is never reached. Moreover, even when an intercalated compound obtained by bringing a stratified mineral into contact with an organic cation has been infinitely swelled using an organic solvent, a portion of the organic solvent is volatilized by the heat in the extruder during the contact with the melted resin, so that the intercalated compound is dispersed in the polymer as it is reverting from an infinitely swelled state to a swelled state. For this reason, in actuality, contact with the melted polymer results as the interlayer distance is shrinking, so that complete dispersion cannot be obtained. In the case of a combination having a large affinity for the organic solvent that employs a non-crystalline resin having good affinity with the organic solvent, dispersion is possible even in the former production method, although it is not complete. However, it is extremely difficult to obtain a good dispersion for crystalline materials. In order to resolve this problem, manipulation of the extruder has also been employed. Namely, as may be seen in Japanese Patent Application, First Publication No. Hei 7-70357, a method has been disclosed in which, when the extruder screw length (L) is expressed as the ratio of screw length/screw diameter (D), i.e. =L/D, the contact time is lengthened by employing an extruder screw length (L) of 45 or more, and the stratified compound infinitely swelled using the organic solvent is dispersed by injection from the lateral surface of the sleeve using a pump. In addition, a mixing and kneading device, such as a banbury mixer, can also be employed as a batch method. However, there is a notable reduction in the treated quantity due to the difficulty in removing the solvent, so that this approach is not economical. The present invention was conceived in order to remedy the costliness associated with using specialized extruders or organic solvents because of the restrictions arising from the aforementioned polymerization reaction. Namely, the present invention provides a compound resin composition in which an intercalated compound is finely dispersed on the nanolevel directly into a resin, this compound resin composition having superior rigidity, and excellent resistance to heat and impact.